Chemical sensors operate by generating a signal in response to the presence of a particular analyte. Graphene-based sensors are one type of chemical sensor that have been increasing in development recently. FIG. 1 illustrates a plan view of a conventional graphene-based sensor for chemical vapor or gas sensing, illustrated as a chemiresistor 100. A sensing material 120 bridges two electrodes 110 and 111. When vapors pass through the sensing material 120 in parts per billion (ppb) range, a change in resistance of the graphene sensing material is observed and a resistance measurement 160 can be taken.
FIG. 2 is a perspective view of a conventional graphene-based sensor 200 configured as a field effect transistor (FET), where a first metal electrode 210 serves as the source, a second metal electrode 211 serves as the drain, and a functionalized graphene channel 220 forms the gate. The electrodes 210 and 211 and the channel 220 are mounted on a dielectric material 230. The sensor 200 shows that graphene-based chemical sensors can be configured as field effect transistors (FETs) to identify specific species and quantify the concentration of the species in a sample.
FIG. 3 is a table listing examples of conventional gas sensors based on graphene. Various graphene hybrids such as epitaxial-G, G-ozone treated, G-exfoliated, G-nanomesh, rGO, G-microfiber and graphene sheets can be used to make chemiresistors, FETs, optical sensors, and conductivity sensors. The table in FIG. 3 lists the target gases, temperatures, detection range, limit of detection (LOD), response sensitivity, response time, and recovery time for the various conventional graphene sensors.
Conventional gas sensors, however, require high power energy sources to sense low levels of chemistry, and the high cost of such equipment has made widespread adoption impractical for many applications. Many conventional systems also rely on adding energy (e.g., using elevated temperatures) to drive the sensing reactions within the sensor and improve the sensitivity. The equipment required for conventional gas sensors is also not readily miniaturized, which limits their use in mobile applications.